1. Field of the Invention
This invention relates to the processing of high performance gun propellants which use an energetic thermoplastic elastomer (TPE) binder in combination with a high energy oxidizer.
2. Technology Background
There is a continuing need for high performance gun propellants which exceed the performance of currently fielded gun propellants and which are easily processed. As an example, the current Army 120 mm tank round gun propellant is a double base propellant (JA2) containing nitrocellulose, nitroglycerine, and an energetic plasticizer. This composition is gelled. If the gun propellant is processed or gelled improperly, the material cannot be easily reprocessed. The gun propellant JA2 has an impetus of about 1190 J/g and a flame temperature of about 3400.degree. K.
Persons skilled in the art have previously proposed using an energetic thermoplastic elastomeric binder instead of nitrocellulose. For instance, U.S. Pat. No. 4,919,737 to Biddle et al. discloses a gun propellant composition containing an energetic thermoplastic elastomeric ("TPE") binder and a high-energy oxidizer. Oxetane polymers, such as copoly-BAMO/AMMO (bisazidomethyloxetane/azidomethyl-methyloxetane) and copoly-BAMO/NMMO (bisazidomethyloxetane/nitraminomethyl-methyloxetane) are disclosed TPE binders. According to Biddle et al. (column 4, lines 26-32), these gun propellants are prepared mixing at a temperature between 100.degree. C. and 125.degree. C., followed by extrusion at a temperature between 70.degree. C. and 130.degree. C. The high temperatures melt the thermoplastic elastomeric binder and allow the propellant to be processed.
A major disadvantage of Biddle et al.'s processing technique is the need to heat the energetic binder and high energy oxidizer to very high processing temperatures. This creates a substantial hazard to equipment and personnel. It also limits the quantity of gun propellant that can be safely processed at any one time. This batch technique can safely process only about 200 grams due to safety and rheological constraints.
It would be a significant advancement in the art to provide a process for manufacturing a high performance gun propellant containing an energetic thermoplastic elastomeric binder and a high-energy oxidizer which enables the safe processing of large quantities of high performance gun propellant.
Such processes of manufacturing a high performance gun propellant are disclosed and claimed herein.